Ionic molecular conjugates of N-acylated derivatives of poly(2-amino-2-deoxy-D-glucose) and polypeptides

ABSTRACT

A copolymer comprising an N-acylated derivative, and a composition comprising said copolymer and a polypeptide, said polypeptide comprising at least one effective ionogenic amine, wherein at least 50 percent, by weight, of said polypeptide present in said composition is ionically bound to said polymer.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of application, applicationSer. No. 09/169,423, filed Oct. 9, 1998, now U.S. Pat. No. 6,479,457which is a continuation-in-part application of application Ser. No.08/929,363, now U.S. Pat. No. 5,821,221, filed Sep. 9, 1997, which is adivisional application of application Ser. No. 08/468,947, now U.S. Pat.No. 5,665,702, filed Jun. 6, 1995.

BACKGROUND OF THE INVENTION

Polymer drug delivery systems have been developed for the controlledrelease of pharmaceutical polypeptides. For example, syntheticpolyesters such as poly(DL-lactic acid), poly(glycolic acid),poly(lactic-glycolic acid), and poly(∈-caprolactone) have been used inthe form of microcapsules, films, or rods to release biologically activepolypeptides. See e.g., U.S. Pat. Nos. 4,767,628 and 4,675,189 and PCTApplication No. WO 94/00148.

In addition to the synthetic polymeric chains, natural polymers andtheir derivatives have been used as components in similar sustainedrelease compositions that dissociate by enzymatic degradation. Oneexample of such natural polymers are those based on chitin, apoly(N-acetylglucosamine). However, since chitin is water insoluble,others have examined solubilizable derivatives which are based primarilyon a partially deacetylated chitin, e.g., chitosan. See e.g., Sanford,P. A. et al., Eds., Advances in Chitin & Chitosan (1992). Althoughchitosan can be found in some fungi, the production of biodegradablechitosan is generally performed synthetically. See Mima, et. al., J.Appl. Polym. Sci. 28 1909-1917 (1983). Synthetic derivatives of chitosanhave also been prepared to alter the polymer's in vivo biologicalcharacteristics. See Muzzarelli, et al., Carbohydrate Res. 207:199-214(1980).

The use of chitin, as well as chitin derivatives, has been proposed in anumber of drug delivery systems. See, e.g., European Patent ApplicationNos. 486,959, 482,649, 525,813 A1, and 544,000 A1; and U.S. Pat. No.5,271,945.

SUMMARY OF THE INVENTION

In one aspect, the present invention features a copolymer including anN-acylated derivative of poly(2-amino-2-deoxy-D-glucose), whereinbetween 1 and 50 percent of the free amines of thepoly(2-amino-2-deoxy-D-glucose) are acylated with a first acyl group,the first acyl group is COE₁ where E₁ is selected from the groupconsisting of C₃₋₃₃ carboxyalkyl, C₃₋₃₃ carboxyalkenyl, C₇₋₃₉carboxyarylalkyl, and C₉₋₃₉ carboxyarylalkenyl, and between 50 and 99percent of the free amines of the poly(2-amino-2-deoxy-D-glucose) areacylated with a second acyl group, the second acyl group is COE₂ whereE₂ is selected from the group consisting of C₁₋₃₀ alkyl, C₂₋₃₀ alkenyl,C₆₋₃₇ arylalkyl, and C₈₋₃₇ arylalkenyl, provided at least one of thefree amines of the derivative is acylated with the first acyl group.

The copolymer preferably has a molecular weight of about 3,000 to 90,000daltons. In other preferred embodiments, over 90 percent of the freeamines of the poly(2-amino-2-deoxy-D-glucose) are acylated with eitherthe first acyl group or the second acyl group. Preferably, between 10and 30 percent of the free amine of the poly(2-amino-2-deoxy-D-glucose)are acylated with the first acyl group. Some of the free hydroxy groups(e.g., between 1 and 30 percent) of the derivative may be acylated witheither the first acyl group or the second acyl group.

In a preferred embodiment, the copolymer is of the formula:

wherein:

R₁, for each individual repeat unit, is selected from the groupconsisting of first acyl group, second acyl group, and H;

R₂, for each individual repeat unit, is selected from the groupconsisting of first acyl group, second acyl group, and H;

R₃, for each individual repeat unit, is selected from the groupconsisting of first acyl group, second acyl group, and H;

R₄ is selected from the group consisting of first acyl group, secondacyl group, and H;

R₅ is selected from the group consisting of first acyl group, secondacyl group, and H;

R₆ is selected from the group consisting of first acyl group, secondacyl group, and H;

R₇ is selected from the group consisting of COH and CH₂OR₈;

R₈ is selected from the group consisting of first acyl group, secondacyl group, and H;

n is between 2 and 200; and

for between 1 and 50 percent of the repeat units, R₁ is first acylgroup, and for between 50 and 99 percent of the repeat units, R₁ issecond acyl group, provided that for at least one of the repeat units,R₁ is first acyl group.

The terms COE₁ and COE₂ stand for —C═O·E₁ and —C═O·E₂, respectively. Thesubstituents carboxyalkyl, carboxyalkenyl, carboxyarylalkyl, andcarboxyarylalkenyl may contain 1-4 carboxylic acid functionalities.Examples of the first acyl group include, but are not limited to,succinyl, 2-(C₁₋₃₀ alkyl)succinyl, 2-(C₂₋₃₀ alkenyl)succinyl, maleyl,phthalyl, glutaryl, and itaconyl. Examples of the second acyl groupinclude but are not limited to, acetyl, benzoyl, propionyl, andphenylacetyl.

The present invention also features a composition including the abovecopolymer and a polypeptide, the polypeptide comprising at least oneeffective ionogenic amine, wherein at least 50 percent, by weight, ofthe polypeptide present in the composition is ionically bound to thepolymer. Preferably, the composition comprises between 5 and 50 percent,by weight, of the polypeptide.

Preferred embodiments of the present invention include a copolymerwherein the first acyl group is succinyl and the second acyl group isacetyl and R₇ is COH or CH₂OH; a composition comprising said copolymerof claim 1 and H-β-D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂ or apharmaceutically acceptable salt thereof, wherein the two Cys are bondedby a disulfide bond, where at least 50 percent, by weight, ofH-β-D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂ or a pharmaceuticallyacceptable salt thereof, present in said composition is ionically boundto said copolymer; a composition comprising the foregoing copolymer anda peptide selected from the group consisting of

or a pharmaceutically acceptable salt thereof, where at least 50percent, by weight, of said peptide or a pharmaceutically acceptablesalt thereof present in said composition is ionically bound to saidcopolymer; a composition comprising the foregoing copolymer and apeptide selected from the group consisting of(p-Glu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH₂), ([D-Ser(t-Bu)⁶,des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt), ([D-Trp⁶, des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt,([des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt), ([D-Ser(t-Bu)⁶, Azgly¹⁰]-LHRH),([D-His(Bzl)⁶, des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt), ([D-Leu⁶, des-Gly-NH₂¹⁰]-LHRH(1-9)NHEt), ([D-Trp⁶, MeLeu⁷, des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt),and ([D-Nal⁶]-LHRH, or a pharmaceutically acceptable salt thereof, whereat least 50 percent, by weight, of said peptide or a pharmaceuticallyacceptable salt thereof, present in said composition is ionically boundto said copolymer; a composition comprising the foregoing copolymer andparathyroid hormone, an analogue thereof or a pharmaceuticallyacceptable salt thereof, where at least 50 percent, by weight, ofparathyroid hormone, an analogue thereof or a pharmaceuticallyacceptable salt thereof, present in said composition is ionically boundto said copolymer.

Further preferred embodiments of the present invention include acopolymer wherein the first acyl group is glutaryl and the second acylgroup is propionyl and R₇ is COH or CH₂OH; a composition comprising theforegoing copolymer and H-β-D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂,wherein the two Cys are bonded by a disulfide bond, where at least 50percent, by weight, of H-β-D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂,present in said composition is ionically bound to said copolymer; acomposition comprising the foregoing copolymer and a peptide selectedfrom the group consisting of

or a pharmaceutically acceptable salt thereof, where at least 50percent, by weight, of said peptide or a pharmaceutically acceptablesalt thereof present in said composition is ionically bound to saidcopolymer; a composition comprising the foregoing copolymer and apeptide selected from the group consisting of(p-Glu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH₂), ([D-Ser(t-Bu)⁶,des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt), ([D-Trp⁶, des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt,([des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt), ([D-Ser(t-Bu)⁶, Azgly¹⁰]-LHRH),([D-His(Bzl)⁶, des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt), ([D-Leu⁶, des-Gly-NH₂¹⁰]-LHRH(1-9)NHEt), ([D-Trp⁶, MeLeu⁷, des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt),and ([D-Nal⁶]-LHRH, or a pharmaceutically acceptable salt thereof, whereat least 50 percent, by weight, of said peptide or a pharmaceuticallyacceptable salt thereof, present in said composition is ionically boundto said copolymer; and a composition comprising the foregoing copolymerand parathyroid hormone, an analogue thereof or a pharmaceuticallyacceptable salt thereof, where at least 50 percent, by weight, ofparathyroid hormone, an analogue or a pharmaceutically acceptable saltthereof, present in said composition is ionically bound to saidcopolymer.

Examples of suitable polypeptides include growth hormone releasingpeptide (GHRP), luteinizing hormone-releasing hormone (LHRH),somatostatin, bombesin, gastrin releasing peptide (GRP), calcitonin,bradykinin, galanin, melanocyte stimulating hormone (MSH), growthhormone releasing factor (GRF), growth hormone (GH), amylin,tachykinins, secretin, parathyroid hormone (PTH), encephalon,endothelin, calcitonin gene releasing peptide (CGRP), neuromedins,parathyroid hormone related protein (PTHrP), glucagon, neurotensin,adrenocorticothrophic hormone (ACTH), peptide YY (PYY), glucagonreleasing peptide (GLP), vasoactive intestinal peptide (VIP), pituitaryadenylate cyclase activating peptide (PACAP), motilin, substance P,neuropeptide Y (NPY), TSH and biologically active analogs thereof. Theterm “biologically active analogs” is used herein to cover naturallyoccurring, recombinant, and synthetic peptides, polypeptides, andproteins having physiological or therapeutic activity. In general, theterm covers all fragments and derivatives of a peptide, protein, or apolypeptide that exhibit a qualitatively similar agonist or antagonisteffect to that of the unmodified, or naturally occurring peptide,protein, or polypeptide, e.g., those in which one or more of the aminoacid residues occurring in the natural compounds are substituted ordeleted, or in which the N- or C-terminal residues has been structurallymodified. The term effective ionogenic amine refers to a free aminepresent on the polypeptide which is capable of forming an ionic bondwith the free carboxylic groups on the copolymer.

Examples of other somatostatin analogs include, but are not limited to,the following somatostatin analogs which are disclosed in theabove-cited references:

H-β-D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂ acetate salt (also known asSOMATULINE™), where the two Cysteines are bonded by a disulfide bond;

H—D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-β-Nal-NH₂;

H—D-Phe-Cys-Tyr-D-Trp-Lys-Thr-Cys-β-Nal-NH₂;

H—D-β-Nal-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

H—D-Phe-Cys-Tyr-D-Trp-Lys-Thr-Pen-Thr-NH₂;

H—D-Phe-Cys-Phe-D-Trp-Lys-Thr-Pen-Thr-NH₂;

H—D-Phe-Cys-Tyr-D-Trp-Lys-Thr-Pen-Thr-OH;

H—D-Phe-Cys-Phe-D-Trp-Lys-Thr-Pen-Thr-OH;

H-Gly-Pen-Phe-D-Trp-Lys-Thr-Cys-Thr-OH;

H-Phe-Pen-Tyr-D-Trp-Lys-Thr-Cys-Thr-OH;

H-Phe-Pen-Phe-D-Trp-Lys-Thr-Pen-Thr-OH;

H—D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-ol;

H—D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

H—D-Trp-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂;

H—D-Trp-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

H—D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂;

H—D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH₂;

H—D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂;

Ac-D-Phe-Lys*-Tyr-D-Trp-Lys-Val-Asp*-Thr-NH₂ (an amide bridge formedbetween Lys* and Asp*);

Ac-hArg(Et)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-D-hArg(Et)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-D-hArg(Bu)-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-D-hArg(Et)₂-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-L-hArg(Et)₂-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-D-hArg(CH₂CF₃)₂-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-D-hArg(CH₂CF₃)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-D-hArg(CH₂CF₃)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Phe-NH₂;

Ac-D-hArg(CH₂CF₃)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NHEt;

Ac-L-hArg(CH₂-CF₃)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-D-hArg(CH₂CF₃)₂-Gly-Cys-Phe-D-Trp-Lys(Me)-Thr-Cys-Thr-NH₂;

Ac-D-hArg(CH₂CF₃)₂-Gly-Cys-Phe-D-Trp-Lys(Me)-Thr-Cys-Thr-NHEt;

Ac-hArg(CH₃, hexyl)-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

H-hArg(hexyl₂)-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-D-hArg(Et)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NHEt;

Ac-D-hArg (Et)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Phe-NH₂;

Propionyl-D-hArg(Et)₂-Gly-Cys-Phe-D-Trp-Lys(iPr)-Thr-Cys-Thr-NH₂;

Ac-D-β-Nal-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Gly-hArg(Et)₂-NH₂;

Ac-D-Lys(iPr)-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-D-hArg(CH₂CF₃)₂—D-hArg(CH₂CF₃)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-D-hArg(CH₂CF₃)₂—D-hArg(CH₂CF₃)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Phe-NH₂;

Ac-D-hArg(Et)₂-D-hArg(Et)₂-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH₂;

Ac-Cys-Lys-Asn-4-Cl-Phe-Phe-D-Trp-Lys-Thr-Phe-Thr-Ser-D-Cys-NH₂;

H-Bmp-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂;

H-Bmp-Tyr-D-Trp-Lys-Val-Cys-Phe-NH₂;

H-Bmp-Tyr-D-Trp-Lys-Val-Cys-p-Cl-Phe-NH₂;

H-Bmp-Tyr-D-Trp-Lys-Val-Cys-β-Nal-NH₂;

H—D-β-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂;

H—D-Phe-Cys-Tyr-D-Trp-Lys-Abu-Cys-Thr-NH₂;

H—D-Phe-Cys-Tyr-D-Trp-Lys-Abu-Cys-β-Nal-NH₂;

H-pentafluoro-D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂;

Ac-D-β-Nal-Cys-pentafluoro-Phe-D-Trp-Lys-Val-Cys-Thr-NH₂;

H-D-β-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-β-Nal-NH₂;

H-D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-β-Nal-NH₂;

H-D-β-Nal-Cys-Tyr-D-Trp-Lys-Abu-Cys-Thr-NH₂;

H-D-p-Cl-Phe-Cys-Tyr-D-Trp-Lys-Abu-Cys-Thr-NH₂;

Ac-D-p-Cl-Phe-Cys-Tyr-D-Trp-Lys-Abu-Cys-Thr-NH₂;

H-D-Phe-Cys-β-Nal-D-Trp-Lys-Val-Cys-Thr-NH₂;

H-D-Phe-Cys-Tyr-D-Trp-Lys-Cys-Thr-NH₂;

cyclo(Pro-Phe-D-Trp-N-Me-Lys-Thr-Phe);

cyclo(Pro-Phe-D-Trp-N-Me-Lys-Thr-Phe);

cyclo(Pro-Phe-D-Trp-Lys-Thr-N-Me-Phe);

cyclo(N-Me-Ala-Tyr-D-Trp-Lys-Thr-Phe);

cyclo(Pro-Tyr-D-Trp-Lys-Thr-Phe);

cyclo(Pro-Phe-D-Trp-Lys-Thr-Phe);

cyclo(Pro-Phe-L-Trp-Lys-Thr-Phe);

cyclo(Pro-Phe-D-Trp(F)-Lys-Thr-Phe);

cyclo(Pro-Phe-Trp(F)-Lys-Thr-Phe);

cyclo(Pro-Phe-D-Trp-Lys-Ser-Phe);

cyclo(Pro-Phe-D-Trp-Lys-Thr-p-Cl-Phe);

cyclo(D-Ala-N-Me-D-Phe-D-Thr-D-Lys-Trp-D-Phe);

cyclo(D-Ala-N-Me-D-Phe-D-Val-Lys-D-Trp-D-Phe);

cyclo(D-Ala-N-Me-D-Phe-D-Thr-Lys-D-Trp-D-Phe);

cyclo(D-Abu-N-Me-D-Phe-D-Val-Lys-D-Trp-D-Tyr);

cyclo(Pro-Tyr-D-Trp-t-4-AchxAla-Thr-Phe);

cyclo(Pro-Phe-D-Trp-t-4-AchxAla-Thr-Phe);

cyclo(N-Me-Ala-Tyr-D-Trp-Lys-Val-Phe);

cyclo(N-Me-Ala-Tyr-D-Trp-t-4-AchxAla-Thr-Phe);

cyclo(Pro-Tyr-D-Trp-4-Amphe-Thr-Phe);

cyclo(Pro-Phe-D-Trp-4-Amphe-Thr-Phe);

cyclo(N-Me-Ala-Tyr-D-Trp-4-Amphe-Thr-Phe);

cyclo(Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-Gaba);

cyclo(Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-Gaba-Gaba);

cyclo(Asn-Phe-D-Trp-Lys-Thr-Phe);

cyclo(Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-NH(CH₂)₄CO);

cyclo(Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-β-Ala);

cyclo(Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-D-Glu)-OH;

cyclo(Phe-Phe-D-Trp-Lys-Thr-Phe);

cyclo(Phe-Phe-D-Trp-Lys-Thr-Phe-Gly);

cyclo(Phe-Phe-D-Trp-Lys-Thr-Phe-Gaba);

cyclo(Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-Gly);

cyclo(Asn-Phe-Phe-D-Trp(F)-Lys-Thr-Phe-Gaba);

cyclo(Asn-Phe-Phe-D-Trp(NO₂)-Lys-Thr-Phe-Gaba);

cyclo(Asn-Phe-Phe-Trp(Br)-Lys-Thr-Phe-Gaba);

cyclo(Asn-Phe-Phe-D-Trp-Lys-Thr-Phe(I)-Gaba);

cyclo(Asn-Phe-Phe-D-Trp-Lys-Thr-Tyr(But)-Gaba);

cyclo(Bmp-Lys-Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-Thr-Pro-Cys)-OH;

cyclo(Bmp-Lys-Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-Thr-Pro-Cys)-OH;

cyclo(Bmp-Lys-Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-Thr-Tpo-Cys)-OH;

cyclo(Bmp-Lys-Asn-Phe-Phe-D-Trp-Lys-Thr-Phe-Thr-MeLeu-Cys)-OH;

cyclo(Phe-Phe-D-Trp-Lys-Thr-Phe-Phe-Gaba);

cyclo(Phe-Phe-D-Trp-Lys-Thr-Phe-D-Phe-Gaba);

cyclo(Phe-Phe-D-Trp(5F)-Lys-Thr-Phe-Phe-Gaba);

cyclo(Asn-Phe-Phe-D-Trp-Lys(Ac)-Thr-Phe-NH—(CH₂)₃-CO);

cyclo(Lys-Phe-Phe-D-Trp-Lys-Thr-Phe-Gaba);

cyclo(Lys-Phe-Phe-D-Trp-Lys-Thr-Phe-Gaba);

cyclo(Orn-Phe-Phe-D-Trp-Lys-Thr-Phe-Gaba);

H-Cys-Phe-Phe-D-Trp-Lys-Thr-Phe-Cys-NH₂;

H-Cys-Phe-Phe-D-Trp-Lys-Ser-Phe-Cys-NH₂;

H-Cys-Phe-Tyr-D-Trp-Lys-Thr-Phe-Cys-NH₂; and

H-Cys-Phe-Tyr(I)-D-Trp-Lys-Thr-Phe-Cys-NH₂.

A disulfide bridge is formed between the two free thiols (e.g., Cys,Pen, or Bmp residues) when they are present in a peptide; however, thedisulfide bond is not shown.

Also included are somatostatin agonists of the following formula:

wherein

A¹ is a D- or L-isomer of Ala, Leu, Ile, Val, Nle, Thr, Ser, β-Nal,β-Pal, Trp, Phe, 2,4-dichloro-Phe, pentafluoro-Phe, p-X-Phe, or o-X-Phe,wherein X is CH₃, Cl, Br, F, OH, OCH₃ or NO₂;

A² is Ala, Leu, Ile, Val, Nle, Phe, β-Nal, pyridyl-Ala, Trp,2,4-dichloro-Phe, pentafluoro-Phe, o-X-Phe, or p-X-Phe, wherein X isCH₃, Cl, Br, F, OH, OCH₃ or NO₂;

A³ is pyridyl-Ala, Trp, Phe, β-Nal, 2,4-dichloro-Phe, pentafluoro-Phe,o-X-Phe, or p-X-Phe, wherein X is CH₃, Cl, Br, F, OH, OCH₃ or NO₂;

A⁶ is Val, Ala, Leu, Ile, Nle, Thr, Abu, or Ser;

A⁷ is Ala, Leu, Ile, Val, Nle, Phe, β-Nal, pyridyl-Ala, Trp,2,4-dichloro-Phe, pentafluoro-Phe, o-X-Phe, or p-X-Phe, wherein X isCH₃, Cl, Br, F, OH, OCH₃ or NO₂;

A⁸ is a D- or L-isomer of Ala, Leu, Ile, Val, Nle, Thr, Ser, Phe, β-Nal,pyridyl-Ala, Trp, 2,4-dichloro-Phe, pentafluoro-Phe, p-X-Phe, oro-X-Phe, wherein X is CH₃, Cl, Br, F, OH, OCH₃ or NO₂;

each R₁ and R₂, independently, is H, lower acyl or lower alkyl; and R₃is OH or NH₂; provided that at least one of A¹ and A⁸ and one of A² andA⁷ must be an aromatic amino acid; and further provided that A¹, A², A⁷and A⁸ cannot all be aromatic amino acids.

Examples of linear agonists to be used in a process of this inventioninclude:

H—D-Phe-p-chloro-Phe-Tyr-D-Trp-Lys-Thr-Phe-Thr-NH₂;

H—D-Phe-p-NO₂-Phe-Tyr-D-Trp-Lys-Val-Phe-Thr-NH₂;

H—D-Nal-p-chloro-Phe-Tyr-D-Trp-Lys-Val-Phe-Thr-NH₂;

H—D-Phe-Phe-Phe-D-Trp-Lys-Thr-Phe-Thr-NH₂;

H—D-Phe-Phe-Tyr-D-Trp-Lys-Val-Phe-Thr-NH₂;

H—D-Phe-p-chloro-Phe-Tyr-D-Trp-Lys-Val-Phe-Thr-NH₂; and

H—D-Phe-Ala-Tyr-D-Trp-Lys-Val-Ala-β-D-Nal-NH₂.

If desired, one or more chemical moieties, e.g., a sugar derivative,mono or poly-hydroxy C₂₋₁₂ alkyl, mono or poly-hydroxy C₂₋₁₂ acylgroups, or a piperazine derivative, can be attached to the somatostatinagonist, e.g., to the N-terminus amino acid. See PCT Application WO88/02756, European Application 0 329 295, and PCT Application No. WO94/04752. An example of somatostatin agonists which contain N-terminalchemical substitutions are:

or a pharmaceutically acceptable salt thereof.

Examples of specific LHRH analogues that can be incorporated in aconjugate or composition of this invention are TRYPTORELIN™(p-Glu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH₂), buserelin([D-Ser(t-Bu)⁶, des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt), deslorelin ([D-Trp⁶,des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt, fertirelin ([des-Gly-NH₂¹⁰]-LHRH(1-9)NHEt), gosrelin ([D-Ser(t-Bu)⁶, Azgly¹⁰]-LHRH), histrelin([D-His(Bzl)⁶, des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt), leuprorelin ([D-Leu⁶,des-Gly-NH₂ ¹⁰]-LHRH(1-9)NHEt), lutrelin ([D-Trp⁶, MeLeu⁷, des-Gly-NH₂¹⁰]-LHRH(1-9)NHEt), nafarelin ([D-Nal⁶]-LHRH and pharmaceuticallyacceptable salts thereof.

The release of the polypeptide from the composition may be modified bychanging the chemical structure of the composition. Increasing themolecular weight of the polymer will decrease the rate of peptidereleased from the conjugate. Increasing the number of carboxylic acidgroups on the polymer will increase the amount of polypeptide ionicallybound to the composition, and consequently, increase the amount ofrelease of the peptide from the conjugate.

The release of the polypeptide may be further modulated through (a)treating the composition with soluble salts of divalent or polyvalentmetallic ions of weak acids (e.g., calcium, iron, magnesium, or zinc);(b) coating the particles with a thin, absorbable layer made of aglycolide copolymer or silicone oil in a spherical, cylindrical, orplanar configuration; or (c) microencapsulating the composition in anabsorbable glycolide copolymer. In one embodiment, the compositioncomprises between 0.01 and 20 percent, by weight, of a polyvalent metal.

Depending on the choice of polypeptide, the compositions can be used totreat any number of disorders. For example, somatostatin, bombesin, GRP,LHRH, and analogs thereof, have been shown to treat various forms ofcancer. Growth factors such as GH, GRF, and GHRP, and analogs thereof,have been shown to stimulate growth in both adolescents and the elderly.Calcitonin, amylin, PTH, and PTHrP, and analogs thereof, have been shownto treat osteoporosis and other bone disorders.

The compositions are designed for parenteral administration, e.g.,intramuscular, subcutaneous, intradural, or intraperitoneal injection.Preferably, the compositions are administered intramuscularly.

The compositions of the invention can be in the form of powder or amicroparticle to be administered as a suspension with a pharmaceuticallyacceptable vehicle (e.g., water with or without a carrier substance suchas mannitol or polysorbate). The compositions may also be compounded inthe form of a rod for parenteral implantation using a trocar, e.g.,intramuscular implantation.

The dose of the composition of the present invention for treating theabove-mentioned diseases or disorders varies depending upon the mannerof administration, the age and the body weight of the subject, and thecondition of the subject to be treated, and ultimately will be decidedby the attending physician or veterinarian. Such an amount of thecomposition as determined by the attending physician or veterinarian isreferred to herein as a “therapeutically effective amount.”

In another aspect, the present invention features a process ofsynthesizing a copolymer, the process comprising the steps of: reactingchitosan with a weak acid to produce a lower molecular weightpolysaccharide; reacting between 1 and 50 percent of the free amines ofthe lower molecular weight polysaccharide with a first acylating agent,the first acylating agent selected from the group consisting of C₄-C₃₄polycarboxyalkane, C₄-C₃₄ polycarboxyalkene, C₈-C₄₀polycarboxyarylalkane, C₁₀-C₄₀ polycarboxyarylalkene, or an acylatingderivative thereof; and reacting between 50 and 100 percent of the freeamine of the lower molecular weight polysaccharide with a secondacylating agent, the second acylating agent selected from the groupconsisting of C₂₋₃₁ monocarboxyalkane, C₃₋₃₁ monocarboxyalkene, C₇₋₃₈monocarboxyarylalkane, C₉₋₃₅ monocarboxyarylalkene, or an acylatingderivative thereof. The reaction of the lower molecular weightpolysaccharide with both the first acylating agent and the secondacylating agent may be measured with an amine detecting agent (e.g.,fluorescamine) to ensure that between 1 and 50 percent of the freeamines of the lower molecular weight polysaccharide are acylated withthe first acylating agent and between 50 and 99 percent of the freeamines of the lower molecular weight polysaccharide are acylated withthe second acylating agent. See, e.g., Bailey, P. D., An Introduction toPeptide Chemistry (Wiley, N.Y.)(1990); Oppenheimer, H, et al. ArchivesBiochem. Biophys. 120:108-118 (1967); Stein, S, Arch. Biochem. Biophys.155:203-212 (1973).

Reacting chitosan with the weak acid (e.g., nitrous acid) cleaves thepolymer, thereby reducing its molecular weight (e.g., 2,500-80,000daltons). In preferred embodiments, the first acylating group and thesecond acylating agent are reacted with the lower molecular weightpolysaccharide successively, e.g., either the first acylating agent isreacted before the second acylating agent is reacted or the secondacylating agent is reacted before the first acylating agent orsimultaneously. As a result of the acylation of the free amines, some ofthe free hydroxy groups of the lower molecular weight polysaccharide maybe acylated. The extent of the acylation of the free hydroxy groups maybe altered by changing the pH or the solvents or agents used during theacylation reactions, or the acylating agents used.

Examples of acylating derivatives include, but are not limited to,anhydrides and N-acylated heterocycles (e.g., imidazoles and pyrazoles).See e.g., Bodansky, et al., The Practice of Peptide Synthesis, 87-150(Springer-Verlag, 1984). The agents polycarboxyalkane,polycarboxyalkene, polycarboxyarylalkane, and polycarboxyarylalkene oracylating derivatives thereof contain, or originate from reactantscontaining, 2-5 carboxylic acid functionalities. The substituentsmonocarboxyalkane, monocarboxyalkene, monocarboxyarylalkane, andmonocarboxyarylalkene contain, or originate from reactants containing,only a single carboxylic acid group. Examples of first acylating agentsinclude, but are not limited to, succinic anhydride, 2-(C₁₋₃₀alkyl)succinic anhydride, 2-(C₂₋₃₀ alkenyl)succinic anhydride, maleicanhydride, glutaric anhydride, itaconic anhydride, and phthalicanhydride. Examples of second acylating agents include, but are notlimited to, acetic anhydride, benzoic anhydride,N,N′-diacetyl-3,5-dimethylpyrazole, N,N-diacetylimidazole, phenylaceticanhydride, propionic anhydride, and butyric anhydride.

In yet another aspect, the present invention features a process ofsynthesizing a composition, the process comprising the steps of:reacting chitosan with a weak acid to produce a lower molecular weightpolysaccharide; reacting between 1 and 50 percent of the free amines ofthe lower molecular weight polysaccharide with a first acylating agent,the first acylating agent selected from the group consisting of C₄-C₃₄polycarboxyalkane, C₄-C₃₄ polycarboxyalkene, C₈-C₄₀polycarboxyarylalkane, C₁₀-C₄₀ polycarboxyarylalkene, or an acylatingderivative thereof; reacting between 50 and 100 percent of the freeamine of the lower molecular weight polysaccharide with a secondacylating agent, the second acylating agent selected from the groupconsisting of C₂₋₃₁ monocarboxyalkane, C₃₋₃₁ monocarboxyalkene, C₇₋₃₈monocarboxyarylalkane, C₉₋₃₅ monocarboxyarylalkene, or an acylatingderivative thereof; neutralizing the acylated lower molecular weightpolysaccharide with a base; and mixing the neutralized lower acylatedmolecular weight polysaccharide with a polypeptide salt, wherein thepolypeptide salt comprises at least one ionogenic amine, to form apolypeptide-copolymer ionic conjugate.

The neutralization step preferably renders the lower molecular weightpolysaccharide emulsifiable or soluble in water. In preferredembodiments, the base is an inorganic base (e.g., sodium hydroxide). Thepolypeptide salt is preferably a weak acid salt (e.g, acetate, lactate,or citrate). The ionic conjugate can be isolated by filtering or bycentrifuging the resulting mixture.

The conjugates of the invention can easily be made into injectablemicrospheres or microparticles, and implantable films or rods, withoutthe need to utilize processing that entails multiphase emulsions.Preferably, the microparticles are manufactured by (a) dissolving thecomposition in an aprotic, water miscible organic solvent; (b) mixingthe organic solvent in water; and (c) isolating the microparticles fromthe water. In preferred embodiments, the organic solvent is chosen fromthe group of acetone, acetonitrile, tetrahydrofuran, dimethylformamide,and dimethyl ethylene glycol.

Other features and advantages of the present invention will be apparentfrom the detailed description and from the claims.

DETAILED DESCRIPTION OF THE INVENTION

The synthesis and use of the copolymer and copolymer-polypeptide ionicconjugates of this invention are well within the ability of a person ofordinary skill in the art. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. Also, all publications, patent applications, patents, and otherreferences mentioned herein are incorporated by reference.

It is believed that one skilled in the art can, based on the descriptionherein, utilize the present invention to its fullest extent. Thefollowing specific embodiments are, therefore, to be construed as merelyillustrative, and not limitative of the remainder of the disclosure inany way whatsoever.

EXAMPLE 1 Depolymerization of Chitosan

Chitosan (Protan, Inc., Portsmouth, N.H.) is dissolved in aqueous aceticacid by stirring with a mechanical stirrer for one day. Nitrogen gas isbubbled through the solution, while an aqueous solution of sodiumnitrite is added. After a half hour, the solution is filtered through asintered glass funnel, under reduced pressure, to remove insolubleparticles which are present in the initial chitosan solution. To thefiltered solution is added an aqueous solution of NaOH, and the solutionis vigorously stirred in methanol to precipitate the polymer. Theresulting precipitate is then filtered and alternately washed five timeswith water and methanol. The precipitate is then dried in a vacuum ovenat 60° C. for two days. The depolymerized chitosan comprises an aldehydegroup at one end of the chain. The aldehyde end group may be reduced toa primary hydroxyl group by reaction NaBH₄. The depolymerized productcan be analyzed by gel permeation chromatography (GPC) to determine bothits molecular weight and molecular weight distribution (MWD) incomparison to Pullulan reference standards. NMR (nuclear magneticresonance) and IR (infra-red) studies can be used to determine theamount of N-acetylation on the depolymerized product.

EXAMPLE 2 Partial Succinylation of Depolymerized Chitosan

The depolymerized chitosan from Example 1 is dissolved in 0.1M aqueousacetic acid. To this solution, methanol is added followed by theaddition of a solution of succinic anhydride in acetone. The resultingsolution is stirred at room temperature for 24 hours. Upon completion ofthe succinylation, the solution is then precipitated into aqueousacetone. The resulting precipitate is collected by centrifugation andwashed five times with methanol. The precipitate is then dissolved in0.5M KOH and dialyzed against water to a pH of 7. The dialyzed solutionis then concentrated under reduced pressure, precipitated in aqueousacetone, and dried in a vacuum oven at 60° C.

To obtain variable levels of succinylation, the extent of the reactioncan be monitored as the acylation proceeds by analyzing for number ofunacylated amine groups. The number of unacylated amine groups can bedetermined by quenching a withdrawn sample of the reaction mixture withan amine detecting agent (e.g., flouorescamine). The amount of aminepresent can be measured spectrophoretically using a standard curve forthe copolymer. Additionally, succinic anhydride, thus, can be addedsuccessively until the desired acylation percentage is achieved Theexact degree of succinylation of the purified product can be determinedusing ¹H NMR spectroscopy and conductometric titration.

EXAMPLE 3 Acetylation of the N-succinylated Chitosan

The partial succinylated sample from Example 2 is dissolved in 0.1Maqueous acetic acid. To this solution, methanol and acetic anhydride isthen added, and the reaction mixture is stirred at room temperature forone day. This solution is then precipitated in aqueous acetone. Theresulting precipitate is collected by centrifugation and washed fivetimes with methanol. The precipitate is then dissolved in 0.1N KOH andis dialyzed against water to a pH of 7. The final solution islyophilized to obtain the final product. The acylation procedure can bemeasured spectrophoretically as discussed in Example 2, and the exactdegree of acylation of the purified product can be determined using ¹HNMR spectroscopy and conductometric titration.

EXAMPLE 4 Preparation of poly(N-acyl-D-glucosamine)-peptide ionicconjugate

The N-succinylated chitosan potassium salt of Example 3 is dissolved inwater. An aqueous solution of the acetate salt of the somatostatinpolypeptide analog SOMATULINE™(D-Nal-c[Cys-Tyr-D-Trp-Lys-Val-Cys]-Thr-NH₂; Kinerton, Dublin, Ireland)is added to the stirred polymer solution. A precipitate forms and isfiltered and dried in a vacuum oven at 40° C.

The polypeptide content of the resulting ionic conjugate can bedetermined by the difference between the amount of initial peptide addedand the amount of free residual peptide contained in the filtrate andrinse solution. The peptide content of the resulting ionic conjugate canbe determined by comparing the carbon/nitrogen ratio of the initialN-succinylated chitosan with that of the resulting ionic conjugate. GPCanalysis can be used to determine molecular weight and MWD, differentialscanning calorimetry (DSC) to determine thermal properties and NMR andIR for chemical identity.

EXAMPLE 5 Homogeneous Depolymerization of Chitosan

Chitosan (Aldrich, Sigma-Aldrich Co. Ltd., Gillingham, Dorset, England,high molecular weight, 10 g) was dissolved in 1L of 0.1M aqueous aceticacid (acetic acid, min. 99.8%, Riedel-de Haën, article number 33209) ina 2L glass beaker with stirring at about 144 rpm using a Heidolphmechanical stirrer (model RZR 2102, Kelheim, Germany). Dissolution wascomplete within ˜4 hours. The inherent viscosity, η_(inh), of the finaldepolymerized chitosan was shown to be dependent on the concentration ofsodium nitrite and the time given for depolymerization, t_(depoly),(Table 1). Inherent viscosity, η_(inh), was determined using aCannon-Fenske routine Ubbelodhe viscometer (Poulten Selfe & Lee ltd.,number 50 of constant 0.003890(mm²/s)/s at 40° C.) with 0.1M acetic acidas solution.

TABLE 1 NaNO₂ (g) T_(depolym) (min) Yield (%) η_(inh) (DL/g) 0.76 3590.8 1.52 0.76 45 87.6 0.98 0.76 55 85.1 0.65 0.152 30 76.7 0.33 0.30430 22.0 0.23 0.304 90 No ppt. —

Sodium nitrite (Aldrich, Sigma-Aldrich Co. Ltd., Gillingham, Dorset,England) in 5-20 ml de-ionized (DI) water (depending on the mass) wasadded to the solution. After the required depolymerization time, thesolution was filtered as quickly as possible through a sintered glassfunnel (25-50μ, Ace Glass Incorporated, Vineland, N.J.) to removeinsoluble matter. To the filtered solution was added NaOH (Aldrich) inDI water (ranging from 4.5 g in 100 ml to 20 g in 400 ml) to quench thedepolymerizing action of NaNO₂. Solution was then added to vigorouslystirred methanol (Labscan, HPLC grade, 300 ml) to precipitate thepolymer. Suspension was spun at 4,000 rpm at 4° C. for 35 min using aSorvall RC 5B plus centrifuge. After spinning, the supernatant wasdecanted off and precipitate was washed with a water/methanol (Labscan,AR grade) mixture (1L, 80:20). Suspension was centrifuged as before,supernatant was again decanted off and depolymerized chitosan waslyophilised in an Edwards Super Modulyo lyophiliser for two daysfollowing overnight refrigeration. The depolymerized chitosan wasfurther dried for 1 day in a vacuum oven (Bioblock Scientific,Strasbourg, −22 mmHg at 30° C.).

EXAMPLE 6 Heterogeneous Depolymerization

Chitosan (18.0 g, as before) and NaNO₂ (as before) were added to a 1Lglass beaker. Trifluoroacetic acid solution (Riedel-de Haën, 23 ml in600 ml DI water, 0.5M) was added to the beaker and the mixture wasstirred using a Heidolph mechanical stirrer (as before). Considerablefizzing was observed on addition of the TFA solution. The solution wasfiltered on a sintered glass funnel (as before). NaOH solution (13.3 gin 165 ml DI water) was added to the filtered solution. The resultingsolution was then added to vigorously stirred methanol (Labscan, HPLCgrade, 300 ml). Centrifugation and washing was carried out as perhomogeneous depolymerization. Table 2 gives results from a series ofdepolymerization experiments.

TABLE 2 NaNO₂ (g) T_(depolym) (min) Yield (%) η_(inh) (DL/g) 9.0 15 24.00.19 9.0 23 20.9 0.13 9.0 45 16.3 0.11 4.5 15 69.5 0.30

With the heterogeneous method, dissolution and depolymerization takeplace simultaneously making it a faster method. Both methods gavesimilar yields (Table 1; 0.33 DL/g with a yield of 76.7% and 0.30 DL/gwith a yield of 69.1%) but with the heterogeneous method largerquantities of chitosan can be used; 18 g as opposed to 10 g. The drieddepolymerized chitosan samples (from examples 5 and 6) with inherentviscosity values in the range 0.23-1.51 DL/g were analysed by ¹³C NMR inaqueous CD₃COOD using a Bruker Spectrospin 400 NMR spectrometer.Chemical shifts of carbons C₁ to C₆ are given in Table 3. The chemicalshift of a particular carbon increases with the inherent viscosity.

TABLE 3 C Type Shift (ppm) C₁ 96.12-99.30 C₂ 54.58-57.44 C₃ 75.20-78.69C₄ 73.55-76.41 C₅ 68.90-71.80 C₆ 58.74-61.77

Elemental analysis was carried out on the depolymerized chitosan samplesfrom examples 5 and 6 (Table 4).

TABLE 4 η_(inh) (DL/g) % Nitrogen Series of Depolymerized Chitosansamples 0.11 3.07 0.13 3.50 0.19 3.40 0.30 5.42 0.33 5.87 0.98 6.78 Lowmol. Wt. Chitosan 8.76 7.11 High mol. Wt. Chitosan 48.50 7.42

The amino content, that is the fraction of chitosan repeating unitscontaining amino groups was obtained by a metachromatic titration usingacid red 88 (Aldrich, dye content ˜75%) by following the method outlinedby Gummow and Roberts (Beryl. D. Gummow, George A. F. Roberts, Makromol.Chem. 186, 1239-1244 (1985), the contents of which are incorporatedherein). Amino content values are given in Table 5.

TABLE 5 η_(inh) (DL/g) Amino Content 48.9  0.83 (Aldrich High mol. wt.Chitosan) 8.76 0.78 (Aldrich Low mol. Wt. Chitosan) 0.98 0.74 0.30 0.56

From % nitrogen values and the amino content values of a series ofdepolymerized chitosan samples in Tables 4 and 5, it is evident that adecrease in η_(inh) is accompanied by a decrease in the amino contentindicating deamination with depolymerization.

Calculations For Glutarylation/Propionylations:

The masses of glutaric and propionic anhydrides required for aglutarylation/propionylation reaction are dependent on the desired molarratio between the two anhydrides, the mass and amino content ofdepolymerized chitosan used. General equations for the masses ofanhydrides for stoichiometric glutarylation/propionylation are givenhere:

Mass of Glutaric Anhydride (GA) required=Desired GA Fraction×MassChitosan×Amino Content×114.1*/161**

*F.W. (GA)

**161=F.W. repeating unit of Chitosan

Mass of Propionic Anhydride (PA) required=Desired PA Fraction×MassChitosan×Amino Content×130.14***/161

***F.W. (PA)

EXAMPLE 7A Glutarylation/Propionylation of Depolymerized Chitosan

Depolymerized chitosan from example 5 with an inherent viscosity of 1.51DL/g was dissolved in 0.1M acetic acid (4.01 g in 150 ml). The aminocontent of this sample was not known at the time but it can be assumedthat it is between 0.74 for depolymerized chitosan of inherent viscosity0.98 DL/g and 0.78 for low mol. wt. chitosan from Aldrich (Table 5).Glutaric anhydride (Aldrich, 95%, 6.0 g) and propionic anhydride(Aldrich, 99+% m, 6.0 g) with glutaric anhydride at an approximately 5.7fold excess and propionic anhydride at an approximately 5.0 fold excessin acetone (Labscan, Dublin, Ireland, AR grade, 29.9 ml, 23.62 g)solution were added to the chitosan solution and left stirringovernight. Resulting solution which was gel-like in nature was pouredinto acetone (Labscan, AR grade, 200 ml) to induce precipitation.Dispersion was spun at 4000 rpm at about 4° C. for about 25 min. Afterspinning, supernatant was washed with methanol (Labscan, HPLC grade, 600ml) and spun as before. Supernatant was decanted off and product waslyophilized following overnight refrigeration. Because of the highexcess of anhydride used, the lyophilized product was washed byredissolving in 0.2M NaOH solution, filtering to remove insoluble matterand precipitation in methanol (Labscan, HPLC grade, 300 ml). Afterspinning at 4000 rpm at about 4° C. for about 25 min, supernatant wasdecanted off and the product was dried by lyophilization (2 days) andvacuum dried for 1 day. % Nitrogen in the final product as determined byelemental analysis was 3.92%.

EXAMPLE 7B Glutarylation/Propionylation of Depolymerized Chitosan

Depolymerized chitosan from example 5 with an inherent viscosity of 0.98DL/g was dissolved in 0.1M acetic acid (1.23 g in 46 ml). The aminocontent of this sample was calculated to be 0.74 (Table 5). Glutaricanhydride (Aldrich, 95%, 1.33 g) and propionic anhydride (Aldrich, 99+%m 1.33 g) with glutaric anhydride at an approximately 3.8 fold excessand propionic anhydride at an approximately 3.3 fold excess in acetone(Labscan, AR grade, 10.1 ml, 8 g) solution was added to the chitosansolution and left stirring overnight. Resulting solution was poured intoacetone (Labscan, AR grade, 80 ml) to induce precipitation. Dispersionwas spun at 4000 rpm at about 4° C. for about 25 min. After spinning,supernatant was washed with methanol (Labscan. HPLC grade, 600 ml) andspun as before. Supernatant was decanted off and product was lyophilizedfollowing overnight refrigeration and then vacuum oven dried (1 day). %Nitrogen of this product as determined from elemental analysis was5.11%.

EXAMPLE 7C Glutarylation/Propionylation of Depolymerized Chitosan

Depolymerized chitosan from example 5 with an inherent viscosity of 0.98DL/g was dissolved in 0.1M acetic acid (4.02 g in 150 ml). The aminocontent of this sample was calculated to be 0.74 (Table 5). Glutaricanhydride (Aldrich, 95%, 4.01 g) and propionic anhydride (Aldrich, 99+%m 4.05 g) with glutaric anhydride at an approximately 3.8 fold excessand propionic anhydride at an approximately 3.3 fold excess in acetone(Labscan, AR grade, 29.4 ml, 23.2 g) solution was added to the chitosansolution and left stirring overnight. Resulting solution was poured intoacetone (Labscan, AR grade, 200 ml) to induce precipitation. Dispersionwas spun at 4000 rpm at about 4° C. for about 25 min. After spinning,supernatant was washed with methanol (Labscan, HPLC grade, 600 ml) andspun as before. Supernatant was decanted off and product was lyophilizedfollowing overnight refrigeration. Because of the high excess ofanhydride used, the lyophilized product was washed by redissolving in0.2M NaOH solution, filtering to remove insoluble matter andprecipitation in methanol (Labscan, HPLC grade, 300 ml). After spinningat 4000 rpm at about 4° C. for about 25 min, supernatant was decantedoff and the product was dried by lyophilization (2 days) and vacuumdried for 1 day. % Nitrogen of this product as determined from elementalanalysis was 5.11%.

EXAMPLE 7D Glutarylation/Propionylation of Depolymerized Chitosan

Depolymerized chitosan from example 6 with an inherent viscosity of 0.30DL/g was dissolved in 0.1M acetic acid (4.01 g in 150 ml). The aminocontent of this sample was calculated to be 0.56. Glutaric anhydride(Aldrich, 95%, 3.0 g) and propionic anhydride (Aldrich, 99+%, 1.0 g) inacetone (Labscan, Dublin, Ireland, AR grade, 29.9 ml, 23.6 g) solutionwas added to the chitosan solution and left stirring overnight.Resulting solution was poured into acetone (Labscan, AR grade, 200 ml)to induce precipitation. Dispersion was spun at 4000 rpm at about 4° C.for about 25 min. After spinning, supernatant was washed with methanol(Labscan, HPLC grade, 600 ml) and spun as before. Supernatant wasdecanted off and product was lyophilized for 2 days following overnightrefrigeration and vacuum dried for 1 day. % Nitrogen of this product asdetermined from elemental analysis was 5.29%.

Glutarylation/Propionylation—A Kinetic Study

6.51 grams of chitosan from example 5 of inherent viscosity, 0.98 DL/gand amino content of 0.74 were dissolved in 0.1M aqueous acetic acid(225 ml). A molar ratio of propionic anhydride to glutaric anhydride of4 was desired in the final product. Glutaric anhydride (Aldrich, 95%,1.443 g) was dissolved in methanol (10 ml) (Labscan, Dublin, Ireland,HPLC grade) and the solution was added to the chitosan solution withstirring at room temperature. After about 2 hours, a 40 ml aliquot ofthe reaction mixture was precipitated in acetone (Labscan, Dublin,Ireland, A.R. grade) spun at 2900 rpm at about 4° C. for about 25 min.Precipitate was washed with methanol (Labscan. HPLC grade) and dried.Another 40 ml aliquot was taken after 4 hours, precipitated, washed anddried as before. Immediately after the 40 ml aliquot was taken (4hours), propionic anhydride solution (Aldrich, 99+%, 2.6489 g inmethanol (Labscan, HPLC grade, 10 ml)) was added to the reactionmixture. After a further 2 hours reaction (equivalent to a totalreaction time of 6 hours from the addition of the glutaric anhydridesolution), the entire mixture was precipitated in acetone (Labscan, ARgrade, 330 ml), dispersion was spun at 4000 rpm at about 4° C. for about30 min in a Sorvall RC plus centrifuge. After spinning, supernatant wasdecanted off and cake was washed twice with methanol (Labscan, HPLCgrade, 400 ml), lyophilized and vacuum oven dried. A metachromatictitration as mentioned in examples 5 and 6 was carried out on the threemodified chitosan samples taken at 2 hours, 4 hours and finally 6 hours.The amino content of these three samples is given in Table 6.

TABLE 6 Time (hours) Amino Content 2 0.91 4 0.43 6 0.10

EXAMPLE 8A Preparation of Poly(N-propionylated, N-glutarylated,N-acetylated-D-glucosamine)-Peptide Ionic Conjugate

1.0038 grams of product from example 7A was dissolved in 20 ml 0.2M NaOHsolution. 450 μl of acetic acid was added to theglutarylated/propionylated solution to bring the pH down to ˜6. Modifiedchitosan solution was then added slowly to a solution of 122.9 mg ofH-β-D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂ acetate salt (also known asSOMATULINE™), where the two Cysteines are bonded by a disulfide bond(Kinerton ltd., Blanchardstown, Dublin, Ireland, B/N 93K2505DL3,Acetate=12.37%, potency=82.68%) in 3.73 g DI water and precipitation wasobserved. The precipitate is also known as a conjugate of the polymerand drug. Dispersion was spun at 2900 rpm at about 4° C. for about 25min using a Sorvall RT 6000 centrifuge. Supernatant was decanted off andretained for further manipulation. Precipitate was placed in arefrigerator. Acetic acid was added to the retained supernatant untilthe pH fell to ˜4. Further precipitation ensued. Dispersion was spun asbefore and then stored in fridge. Precipitate from first and secondcentrifuges were lyophilized, vacuum oven dried and yields obtained wererespectively 31.7% (356.9 mg) and 36.4% (409.6 mg) with a combined yieldof 68.1%. Elemental analysis was carried out on the combined product. %Nitrogen as determined from elemental analysis for the combinedconjugate was 4.60% and using the % nitrogen of 3.92% for product fromexample 7A, the % loading of SOMATULINE™ was calculated to be 6.7%.

In vivo assay: Conjugate of example 8A was suspended in salinecontaining Tween® 20 (1%) and injected at 7.5 mg peptide equivalent perrat. SOMATULINE™ levels in rat plasma induced by this conjugate werebetween a maximum value of 636,757+/−124,759 pg/ml and a minimum valueof 863+/−145 pg/ml over a 15 day period, see Table 7.

EXAMPLE 8B Preparation of Poly(N-propionylated, N-glutarylated,N-acetylated-D-glucosamine)-Peptide Ionic Conjugate

1.0010 grams of product from example 7A was dissolved in 12 ml 0.2M NaOHsolution. 250 μl of acetic acid was added to theglutarylated/propionylated solution to bring the pH down to ˜6. Modifiedchitosan solution was then added slowly to a solution of 120.3 mg ofSOMATULINE™ (Kinerton ltd., Blanchardstown, Dublin, Ireland, B/N93K2505DL3, Acetate=12.37%, potency=82.68%) in 2.87 g DI water andprecipitation was observed. Because of the lower volume of NaOH solutionused, the resulting solution was extremely viscous. Dispersion was spunat 2900 rpm at about 4° C. for about 25 min using a Sorvall RT 6000centrifuge. Supernatant was decanted off and retained for furthermanipulation. Precipitate was placed in a refrigerator. Acetic acid wasadded to the retained supernatant until the pH fell to ˜4. Furtherprecipitation ensued. Dispersion was spun as before and then stored in arefrigerator. Precipitate from first and second centrifuges werelyophilized, vacuum oven dried and yields obtained were respectively53.5% (600.4 mg) and 20.9% (234.8 mg) with a combined yield of 74.4%.Elemental analysis was carried out on the combined product. % Nitrogenas determined from elemental analysis for the combined conjugate was4.30% and using the % nitrogen of 3.92% for product from example 7A, the% loading of SOMATULINE™ was calculated to be 4.0%.

In vivo assay: Conjugate was suspended in saline containing Tween® 20(1%) and injected at 7.5 mg peptide equivalent per rat. SOMATULINE™levels in rat plasma induced by this conjugate were between a maximumvalue of 545,367+/−69,445 pg/ml and a minimum value of 1134+/−325 pg/mlover a 15 day period, see Table 7.

EXAMPLE 8C Preparation of Poly(N-propionylated, N-glutarylated,N-acetylated-D-glucosamine)-Peptide Ionic Conjugate

1.0190 grams of example 7B was dissolved in 20 ml 0.2M NaOH solution.200 μl of acetic acid was added to the glutarylated/propionylatedsolution to bring the pH down to ˜6. Modified chitosan solution was thenadded slowly to a solution of 102.1 mg of SOMATULINE™ (Kinerton ltd.,Blanchardstown, Dublin, Ireland, B/N 93K2505DL3, Acetate=12.37%,potency=82.68%) in 2.56 g DI water and precipitation was observed.Dispersion was spun at 2900 rpm at about 4° C. for about 25 min using aSorvall RT 6000 centrifuge. Supernatant was decanted off and retainedfor further manipulation. Precipitate was placed in refrigerator. Aceticacid was added to the retained supernatant until the pH fell to ˜4.Further precipitation ensued. Dispersion was spun as before and thenstored in a refrigerator. Precipitate from first and second centrifugeswere lyophilized, vacuum oven dried and the combined yield obtained was74% (827.1 mg). % Loading of SOMATULINE™ in this conjugate was taken tobe similar to the % Loading of SOMATULINE™ example 4D i.e., 14%.

In vivo assay: Conjugate was suspended in saline containing Tween® 20(1%) and injected at 7.5 mg peptide equivalent per rat. SOMATULINE®levels in rat plasma induced by this conjugate were between a maximumvalue of 168.141+/−90,972 pg/ml and a minimum value of 1000 pg/ml over a9 day period, see Table 7.

EXAMPLE 8D Preparation of Poly(N-propionylated, N-glutarylated,N-acetylated-D-glucosamine)-Peptide Ionic Conjugate

1.0149 grams of example 7C was dissolved in 15 ml 0.05M NaOH solution.The molarity of the NaOH in this example is lower than that of example8C. 200 μl of acetic acid was added to the glutarylated/propionylatedsolution to bring the pH down to ˜6. Modified chitosan solution was thenadded slowly to a solution of 125.2 mg of SOMATULINE™ (Kinerton ltd.,Blanchardstown, Dublin, Ireland, B/N 93K2505DL3, Acetate=9.37%,potency=80.68%) in 3.0 g DI water and precipitation was observed.Dispersion was spun at 2900 rpm at about 4° C. for about 25 min using aSorvall RT 6000 centrifuge. Supernatant was decanted off and retainedfor further manipulation. Precipitate was placed in fridge. Acetic acidwas added to the retained supernatant until the pH fell to ˜4. Furtherprecipitation ensued. Dispersion was spun as before and then stored infridge. Precipitate from first and second centrifuges were lyophilized,vacuum oven dried and the combined yield obtained was only 24% (270 mg).Elemental analysis was carried out on the combined product. % Nitrogenas determined from elemental analysis for the combined conjugate was6.34% and using the % nitrogen of 5.11% for product from example 7C, the% loading of SOMATULINE™ was calculated to be 14.0%.

In vivo assay: Conjugate was suspended in saline containing Tween® 20(1%) and injected at 7.5 mg peptide equivalent per rat. SOMATULINE™levels in rat plasma induced by this conjugate were between a maximumvalue of 192,419+/−112,621 pg/ml and a minimum value of 1000/ml over a12 day period, see Table 7.

EXAMPLE 8E Preparation of Poly(N-propionylated, N-glutarylated,N-acetylated-D-glucosamine)-Peptide Ionic Conjugate

2.0 grams of example 7D was dissolved in 28 ml 0.05M NaOH solution.Chitosan solution was then added slowly to a solution of 246.0 mg ofSOMATULINE™ (Kinerton ltd., Blanchardstown, Dublin, Ireland, B/N93K2505DL3, Acetate=9.37%, potency=80.68%) in 6.0 g DI water andprecipitation was observed. Dispersion was spun at 2900 rpm at about 4°C. for about 25 min using a Sorvall RT 6000 centrifuge. Supernatant wasdecanted off. Precipitate was washed with 24 ml DI water and spun asbefore. Precipitate was then placed in a refrigerator. Elementalanalysis was carried out on the product. % Nitrogen as determined fromelemental analysis for the conjugate was 6.6% and using the % nitrogenof 5.29% for product from example 7D. The % loading of SOMATULINE™ wascalculated to be 15%.

In vivo assay: Conjugate was suspended in saline containing Tween® 20(1%) and injected at 3.75 mg peptide equivalent per rat. SOMATULINE™levels in rat plasma induced by this conjugate were between a maximumvalue of 145,429±122,743 pg/ml and a minimum value of 500±159/ml over a10 day period, see Table 7.

OTHER EMBODIMENTS

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, that the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Otheraspects, advantages, and modifications are within the claims.

TABLE 7 Time Example No. 6 h Day 2 Day 3 Day 5 Day 10 Day 15 8A 538257 ±43374  636757 ± 124759  74764 ± 14316 43353 ± 2582  1996 ± 217   863 ±145 8B 495495 ± 67884  545367 ± 69445  60238 ± 6719 42132 ± 4762  1448 ±238  1134 ± 325 8C 168141 ± 90972  114160 ± 48759  26174 ± 9103  5118 ±2855 88 ± 95 <21 8D 192419 ± 112621 175009 ± 107126 106996 ± 20387 27883± 12858 1532 ± 1178 116 ± 0   8E* 145429 ± 122743 110486 ± 65496   21546± 11359 11420 ± 4782  500 ± 159 <21 *Example 8E was injected at a doseof 3.75 mg of peptide equivalent per rat.

What is claimed is:
 1. A composition comprising a copolymer and apeptide which said copolymer is an N-acylated derivative ofpoly(2-amino-2-deoxy-D-glucose) in which between 1 and 50 percent of thefree amines of said poly(2-amino-2-deoxy-D-glucose) are acylated with afirst acyl group, said first acyl group is COE₁ where E₁ is selectedfrom the group consisting of C₃₋₃₃ carboxyalkyl, C₃₋₃₃ carboxyalkenyl,C₇₋₃₉ carboxyarylalkyl, and C₉₋₃₉ carboxyarylalkenyl, and between 50 and99 percent of the free amines of said poly(2-amino-2-deoxy-D-glucose)are acylated with a second acyl group, said second acyl group is COE₂where E₂ is selected from the group consisting of C₁₋₃₀ alkyl, C₂₋₃₀alkenyl, C₆₋₃₇ arylalkyl, and C₈₋₃₇ arylalkenyl, provided at least oneof the free amines of said poly(2-amino-2-deoxy-D-glucose) is acylatedwith said first acyl group and wherein said peptide isH-β-D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂ or a pharmaceuticallyacceptable salt thereof, present in said composition is ionically boundto said copolymer, wherein said first acyl group is succinyl and saidsecond acyl group is acetyl.
 2. A composition comprising a copolymer anda peptide wherein said copolymer is an N-acylated derivative ofpoly(2-amino-2-deoxy-D-glucose), in which between 1 and 50 percent ofthe free amines of said poly(2-amino-2-deoxy-D-glucose) are acylatedwith glutaryl and between 50 and 99 percent of the free amines of saidpoly(2-amino-2-deoxy-D-glucose) are acylated with propionyl, provided atleast one of the free amines of said poly(2-amino-2-deoxy-D-glucose) isacylated with glutaryl and wherein said peptide isH-β-D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂ or a pharmaceuticallyacceptable salt thereof, in which the two Cys are bonded by a disulfidebond, where at least 50 percent, by weight, ofH-β-D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH₂ or pharmaceuticallyacceptable salt thereof, present in said composition is ionically boundto said copolymer.